Burner control apparatus



March 1963 w. B. HAMELINK 3,0 ,8 3

BURNER CONTROL APPARATUS Filed Jan. 30. 1961 2 Sheets-Sheet 1 STOP START FLAME DETECTOR 2o so JNVENTOR.

WILLIAM D. HAMELINK A TTOR/VE Y March 26, 1963 w. B. HAMELINK BURNER CONTROL APPARATUS Filed Jan. 30. 1961 2 Sheets-Sheet 2 FAN W 37 Fl- 2 H 3L3 o a FLAME 1 DETECTOR PURGE PILOT TRIAL T MAIN BURNER TRIAL moorn-nod:

O I O 2O 3O 4O 5O 6O 7O I00 IlO I20 TIME IN SECONDS INVENTOR.

WILLIAM D. HAMELINK BY Fl AT TORNEY United States Patent 3,082,813 BURNER CONTROL APPARATUS William B. Hamelink, Richfield, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Filed Jan. 30, 1961, Ser. No. 85,873 7 Claims. (Cl. 158-28) The present invention is concerned with an improved burner control apparatus and particularly with a burner control apparatus providing a prepurge operating cycle, wherein a safety cutout means of the burner control apparatus is maintained inoperative, while the operativeness of the safety cutout means is checked, and is operative only at the end of the prepurge period.

In the art of burner control apparatus, it is usual practice to provide a prepurge time period during which combustion air is supplied to the firebox wherein a fuel burner unit is located, to purge the firebox of unburned fuel prior to an attempt to establish combustion at the fuel burner unit. This purge period is provided to purge the firebox of any accumulation 'of combustible fuel, to thereby prevent a disastrous explosion.

The apparatus of the present invention pertains'to th general above mentioned type of control apparatus and incorporates as the inventive concept a structural arrangement whereby the electrically energizable actuator of the safety cutout means is checked for electrical continuity during the prepurge period, but is operatively energized only at the end of the prepurge period. With such a construction, should the electrically energizable actuator of the safety cutout means open circuit, the burner control apparatus is rendered inoperative during the prepurge period. Thus, in the event that the safety cutout means becomes inoperative at any time during the prepurge period, no raw fuel is supplied to the firebox and the occurrence of an explosion due to an accumulation of raw fuel is completely averted.

As a further recognition of the state of the prior art, it should be mentioned at this point that the prior art initially checks the electrical continuity of the safety cutout means actuator but does not maintain this check continuously during the prepurge period. An actuator, for example the heater for a bimetal, may have electrical continuity upon initial energization thereof. However, this heater may later burn out and open circuit. The apparatus of the present invention, since it checks the electrical continuity of this heater during the entire prepurge period, responds to such an open circuiting of the heater to render the control apparatus inoperative. Thus, by way of the present invention, I have provided a means of sensing the inoperativeness of the safety cutout means actuator if such inoperativeness occurs during the prepurge period. As a result, the burner control apparatus of my invention eliminates a faulty condition which can occur in prior art burner control apparatus.

The present invention also contemplates the use of an electronic flame detector. As is well known, it is de sirable to provide a component checking means to sense an unsafe failure of the electronic flame detector on initial start-up of the apparatus. By definition, an unsafe failure is a failure which causes the flame detector to indicate flame when in fact no flame is present. The present invention utilizes a normally closed switch of the flame detector in series with the safety cutout means actuator such that a premature opening of this switch during the prepurge period, due to a component failure, renders the apparatus inoperative to subsequently energize the fuel burner unit.

My invention will be apparent to those skilled in the art upon reference to the following specification, claims I and drawings, of which:

FIGURE 1 is a conventional schematic wiring diagram showing my burner control apparatus connected to control the components of the fuel burner unit,

FIGURE 2 is a showing of the apparatus of FIGURE 1, using a somewhat different wiring diagram, to simplify the showing of FIGURE 1, and

FIGURE 3 is a bar graph showing the time relationship of the operation of the switches of the timer of FIGURES l and 2.

Referring specifically to FIGURES 1 and 2, FIGURE 1 differs from the showing of FIGURE 2 mainly in that various switches of the relays and the timer, as well as the specific construction of the safety cutout means and the fuel burner unit, are physically associated in the drawing of FIGURE 1 to point up not only their physical construction but the electrical operation and properties of the components. In FIGURE 2, these various components are not presented to show their physical relationship but are presented to more clearly show the electrical circuits which result and which are controlled by operation of the various components. However, like reference numerals are utilized in FIGURES 1 and 2 to provide convenient reference between the figures. The apparatus of FIGURE 1 will be briefly described and the operation thereof will be described more completely with reference to FIGURE 2.

Referring specifically to FIGURE 1, the burner control apparatus is controlled by means of a start-stop station designated generally by means of the reference numeral 10. As will be apparent, the start button is effective to control the energization of a main control relay designated by means of the reference numeral 11. This relay is provided with an electrically energizable winding 12, normally open switches 13, 14, 15 and 16, and a normally closed switch 17.

The energization of relay 11 is supervised or controlled by a safety cutout means or safety switch designated generally by means of reference numeral 20. This safety cutout means is of thetime delay type and specifically provides a bimetal operator 21 associated with an electrically energizable actuating heater 22 controlling a normally closed switch 23. Reference numeral 24 identifies a reset button.- As indicated in FIGURE 1, bimetal 21 is operative upon heating to cause the upper portion thereof to move to the right out from under the switch blades associated with switch 23 to thereby allow this switch to open, whereupon the switch may be reset to its normally closed position after cooling of the bimetal 21, the resetting being accomplished by depressing reset button 24.

Reference numeral 25 designates an electronic flame detector which receives its operating voltage from a transformer 26 whose primary winding is connected to a pair of power line conductors 27 and 28. The input of flame detector 25 includes a pair of terminals 29 and 30 which are connected to flame sensing means in the form of a. photocell 31. The output of flame detector 25 includes a pair of terminals 32 and 33 conected to energize a flame relay 34 having an electrically energizable winding 35,

normally open switches 36 and 37 and a normally closed switch 38.

Reference numeral 40 identifies a further relay having I an electrically energizable winding 41 and a normally open switch 42. I Reference numeral 43 identifies a timer included within a broken line box. This timer is provided with an electrically energizable actuator 44 and includes a pluralityof switches. These switches, identified by the letters A-H inclusive, are operatively associated with the actuator 44 to be controlled in a time sequence upon energization of this actuator, this time sequence being shown in bar graph form in FIGURE 3. In FIGURE 3, the dark portion of the bar indicates the closed condition of the respective switch, while the open portion indicates the open condition of the particular switch. In actual practice, timer 43 may consist of a small synchronous motor, identified by reference numeral 44, which controls a shaft carrying a number of cams, usually adjustable to provide varying time periods of which FIGURE 3 can be considered to be a representative condition, and the cams controlling the operation of the switches A-H inclusive.

Reference numeral 58 designates generally a fuel burner unit which is adapted to be located in the firebox of a furnace, not shown. The components of the fuel burner unit Sll include a pilot burner 51 with its pilot valve 52, and ignition electrode 53 connected to an ignition transformer 54, a main fuel burner housing 55 commuicating with a chamber including a blower or fan and motor 56 and a main fuel valve 57. As is well known, energization of the ignition transformer 54 and the pilot valve 52 is effective to establish a pilot flame at the pilot burner 51. This pilot flame is sensed by the flame sensing means 31, and as a result thereof the main valve 54 is energized to admit fuel to the main fuel burner, which fuel is ignited by the pilot flame. The fan 56 is effective to supply combustion air to the main fuel burner and is also effective to purge the firebox of unburned fuel prior to the attempt to establish combustion at either the pilot burner 51 or the main burner 55.

Thus far, the general overall construction of my improved burner control apparatus as shown in FIGURE 1 has been described, FIGURE 1 showing in a diagrammatic form not only the physical construction of the various components but also the electrical interconnection of these components. For purposes of simplification, the flame detector 25 is shown in block diagram form and this flame detector may, for example, be of the orm shon in the Richard S. Feigal Patent 2,556,961, issued June 12, .1951.

The more detailed operation of my improved burner control apparatus will now be described in connection with the showing of FIGURES 2 and 3. The apparatus as shown in FIGURE 2 is in the standby condition wherein operating voltage is applied to the conductors 27 and 28 from a source of alternating supply voltage, not shown. Main burner control relay 1 1 is de-energized and a flame is not present at the fuel burner unit 50 of FIGURE 1. As a result, flame relay 34 is de-energized and the further relay 40 is de-energized. The timer motor 44 is deenergized and the associated switches of the timer are in the respective conditions as indicated at the zero time point of FIGURE 3. Thus, switches A, E, F and H are closed, and switches B, C, D and G are open.

If it is now assumed that there is a need for operation of the fuel burner unit, the start button is depressed to close a circuit which can be traced from power line conductor 27 through the stop button, the start button, timer switch A, normally closed switch 38 of flame relay 34, the electrically energizable actuator 22 of safety cutout means 20, to the lower terminal of winding 62 of transformer 60, the upper terminal of winding 62, normally closed switch 23 of the safety cutout means 20, winding 12 of main control relay 11, and conductor 63 to the other power line conductor 28. From this circuit it can be seen that actuator 22 is connected in series with winding 12.

The impedances of these two elements (22 and 11) are selected, with a given line voltage, such that so long as these two elements are connected in the above mentioned series circuit, heater 22 is operatively de-energized while winding 12 of main control relay 11 is opcratively energized to cause its switches to move to their actuated position. Furthermore, it can be seen from this above traced circuit that in order for the series circuit to be complete the timer must be in its start position wherein the start interlock switch A is closed, the flame relay 34 must be in a condition indicating the absence of flame at the fuel burner unit to thereby close its switch 38, the

safety cutout means 20 must be in a condition to close its switch 23, and the heater 22 of the safety cutout means, which at this time is not opcratively energized, must have electrical continuity, in order for winding 12 of the main burner control relay 11 to be opcratively energized. Should the heater 22 of the safety switch 20 be open circuited at the time the start button is pushed, or should the heater subsequently open circuit during the prepurge period, which will be described, then winding 12 of relay 111 is immediately de-energized to de-energize all components of the fuel burner unit, as will be apparent.

Energization of the winding of relay 11 is effective to cause its respective switches 13 through 17 to move to their actuated positions wherein switches 13 through 16 are closed and switch 17 is opened. The closing of switch 14 completes a circuit which shunts the start button and the timer start interlock switch A. Thus, the start button may now be released and the above traced circuit is maintained through switch 14 of relay 11. The closing of switch 16 is effective to energize winding 41 of the further relay 40 and to also energize actuator 44 of timer 43. The energizing circuit for winding 41 can be traced from power line conductor 27 through switch 16 of relay 11, relay winding 41, and conductor 63 to the other power line conductor 28. The energizing circuit for actuator 44 of timer 43 can be traced from power line conductor 27 through switch 16 of relay 14, timer switch F, timer actuator 44, and conductor 63 to power line conductor 28.

Energization of winding 41 is effective to cause the single switch 42 of relay 40 to move to a closed condition and complete an energizing circuit for fan 56 of the fuel burner unit 50. This energizing circuit can be traced from power line conductor 27 through switch 42. and fan 56 to the other power line conductor 28.

Energization of the actuator 44 of timer 43 is effective to cause the timing function to begin, it being noted from FIG. 3 that the first switching to take place takes place at the five second time interval point.

Furthermore, as indicated in FIGURE 3, the interval from zero to 40 seconds is the purge time period and it is during this interval that only fan 56 of the fuel burner unit 50 is energized, to thereby purge the firebox of unburned fuel which may have accumulated, for one reason or another, within the firebox.

Considering the operation of the apparatus of FIGURE 2 at the five second interval, at this interval the start interlock switch A of the timer, which switch is now shunted by switch 14 of the main burner control relay 11, is actuated to an open position. Also, switch B is actuated to a.- closed position. Switch B shunts switch 16 of the main burner control relay 11 and is effective to maintain winding 41 of the further relay 40 energized, as well as to maintain actuator 44 of the timer 43 energized independent of the state of energization of the main burner control relay 11, it being recognized, however, that the main burner control relay 11 normally remains in an actuated position to maintain switch 16 in a closed condition.

It is also noted that switch 38 of the flame relay is in series with the winding of main control relay 11 during this prepurge period. As a result, should a component failure occur within flame detector 25 causing an unsafe failure, flame relay 34 is energized to open switch 38 and de-energize main control relay 11, thus providing a component check feature. With relay 11 de-energized, switch 15 opens and the circuit to the main valve 57 and pilot valve 52 cannot be completed. Normally, however, such a component failure does not occur.

At the end of the purge period, that is at the 40 second time interval point of FIGURE 3, switches C and G are acniated to a closed position. Switch C, in the closed position, is effective to establish an energizing circuit for the pilot valve 52 and the ignition transformer 54 of the fuel burner unit 50. This energizing circuit can be traced from power line conductor 27 through the stop button, closed switch 15 of main burner control relay 11, timer switch E, timer switch C, and pilot valve 52 and ignition transformer 54 in parallel to the other power line conductor 28. Thus, a pilot flame is normally established at the pilot burner 51 of the fuel burner unit 50.

The closing of switch G is effective to not only establish a maintaining circuit for winding 12 of the main burner control relay 11, but is also effective to establish an initial energizing circuit for actuating heater 22 of the safety cutout means 20 to thereby operatively energize this actuator for the first time during the sequence of operation of my improved burner control apparatus. Considering the maintaining circuit for winding 11, this circuit can be traced from power line conductor 27 through the stop button, closed switch 14 of the main burner control relay 11, timer switch G, closed switch 13 of the main burner control relay 11, normally closed switch 23 of the safety cutout means 20, relay winding 12, and conductor 63 to the other power line conductor 28.

7 Considering the circuit which for the first time operatively energizes the actuating heater 22 of safety cutout means 20, this circuit can be traced from the lower terminal of transformer winding 62 through heater 22, normally closed switch 38 of the flame relay 34, timer switch G, and closed switch 13 of the main burner control relay 11 to the upper terminal of winding 62. Thus, it can be seen that actuating heater 22 of the safety cutout means 20 is connected across the source of voltage as formed by winding 62 forming a source of supply voltage to operatively energize heater 22.

As has been pointed out, now that fuel is supplied to the fuel burner unit as a result of energization of pilot valve 52 it is desirable to operatively energize actuator 22 of the safety cutout means.

Normally, a pilot flame is established at pilot burner 51 during the pilot trial period which exists from the 40 second to the 50 second time point as shown in FIGURE 3, thus allowing a ten second pilot trial period. During this time a pilot flame is established and flame sensing means 31 is effective through flame detector 25 to energize relay 34. The energizing circuit for relay 34 eX- tends from terminal 32 through winding 35, closed timer switch H, to terminal 33. Energization of winding 35 is effective to cause the switches 36, 37 and 38 to move to their actuated positions wherein switches 36 and 37 close and swtich 38 opens.

' The opening of switch '38 opens the energizing circuit for actuating heater 22 of safety cutout means 20. The closing of switch 36 is effective to place a shunt circuit around timer switch E, which switch is located in the circuit to initially energize igntion transformer 54 and the pilot valve 52. Thus, a maintaining circuit is established for these components. 51 he closing of switch 37 is effective to shunt timer switch H, which switch is in the initial energizing circuit for the winding of relay 35, and thus a maintaining circuit is established for this winding.

Consider now the 50 second time point on the bar graph of FIGURE 3. At this point, timer switches E and H open while switch D closes. The closing of switch D completes an energizing circuit for main valve 57 while the opening of switch E opens the initial energizing circuit for pilot valve 52 and ignition 54. Thus, the main valve is energized through a circuit which can be traced from power line conductor 27 through the stop button, closed switch 15 of the main burner control relay 11, closed switch 36 of the flame relay 35, timer switch D, and main valve 57 to the other power line conductor 28. As can be seen from FIGURE 3, the time period from 50 to 80 seconds is designated the main burner trial period, and it is during this period that the pilot valve, the ignition transformer, and the main valve are energized in an attempt to establish flame at the main burner '55. During this period, the flame at main burner 55 must be established in a stable manner and therefore the opening of timer switch H at the fifty second interval places the energizing of flame relay 34 under the control of its switch 37, now closed. Thus, if an unstable main flame has been established and flame sensing means 31 detects even a momentary absence of flame, then flame relay 35 is de-energized and cannot be re-energized due to the fact that not only its switch 37 is open, but likewise timer switch H is open.

Normally, however, a flame is established at the main fuel burner during the main burner trial period.

Considering now the operation of the apparatus at the second interval, at this point timer switch C opens. The opening of timer switch C is effective to de-energize pilot valve 52 and ignition transformer 54, thus leaving the main valve 57 energized and placing flame sensing means 31 in a condition to monitor the presence or absence of flame at the main fuel burner unit 55. As has been pointed out, should the flame fail even momentarily, then the flame relay 34 is de-energized and is maintained de-energized due to the fact that not only is its own switch 37 open, but likewise timer switch H is open. De-energization of flame relay 34 at any time is also effective to open its switch 36 and since the timer switch E is open at this time, the opening of switch 36 immediately deenergizes main valve 57 to prevent an accumulation of unburned fuel at the firebox.

My improved burner control apparatus continues to function in this mode of operation until the second time interval point is reached. At this point, timer switch F opens. Opening of switch F is effective to de-energize the actuator 44 of timer 43 and the timer then stops in this position. This is the running position of the burner control apparatus and in this position the fan 56 and the main valve 57 of the fuel burner unit 50 are energized. The presence of combustion at the fuel burner unit is monitored by flame sensing means 31 and so long as combustion is present, flame relay 35 is energized. Likewise, until the stop button is depressed, main burner control relay 1E1 is energized and further relay 40 is energized. The timer is stopped at a position wherein its switches B, D and G are closed while its switches A, C, E, F and H are open.

Assume now that the end of a period of operation of the fuel burner unit is signalled by depressing the stop button. Depressing of this button immediately de-energizes the main burner control relay 11 to thus cause its switches 13 through 17 to assume a position as shown in FIGURE 1. The opening of switch 15 is effective to de energize main valve 57. The opening of switch 14 is effective to remove the shunt circuit which was established around the start button and the timer start interlock switch A, thus preventing a restart of the burner control apparatus until the timer has returned to its start position to close switch A. The closing of switch 17 is effective to establish an energizing circuit for the actuator 44 of timer 43 to restart the timer, this circuit being traced from power line conductor 27 through timer switch B, switch 17 of the main burner control relay 11, actuator 44 of the timer, and conductor 63 to the other power line conductor 28. It will be noted at this time that relay 40 remains in its energized position to maintain fan 56 energized and to thus provide a post-purge period during which the firebox is purged of any unburned fuel vapors as well as any remaining products of combustion.

As timer 43 continues to operate from the 105 second interval to the second interval, timer switches D and G are opened. The opening of timer switch D is directly in series with the main valve 57 whereas switch G is in series with the already open switch 13 of the main burner 7 button. The closing of switches F and H close respective circuits which are operated during a subsequent restart of the fuel burner unit 50, as above described.

From the above description, tracing a complete cycle of operation of the apparatus of this present invention, it can be seen that I have provided an improved burner control apparatus which utilizes a timer to provide a prepurged period and in which the actuator 22 of the safety cutout means 20 is checked as to its operativeness during the prepurge period. However, the safety cutout means 20 is not operatively energized until the end of this purge period. Also, my improved burner control apparatus provides a means whereby a component failure during the prepurge period is effective to prevent subsequent energization of the fuel supplying components of the fuel burner unit.

Other modifications of the present invention will be apparent to those skilled in the art, and it is therefore intended that the scope of the present invention be limited solely by the scope of the appended claims.

I claim as my invention:

1. Burner control apparatus for use with a fuel burner unit having a fuel burner and a blower to supply air thereto for purposes of first purging the fuel burner unit of unburned fuel prior to the ignition of the fuel burner and to thereafter supply combustion air, the apparatus comprising; control means having an electrically energizable actuator and adapted upon energization thereof to-energize the blower; safety cutout means having an electrically energizable actuator and having means adapted to be actuated after a time period of operative energization of said actuator; a source of voltage, energizing circuit means for said control means actuator connecting said safety cutout means actuator in series with said control means actuator to said source of voltage, the impedances of said actuators being such that while connected in series said safety cutout means actuator is maintained operatively deenergized while said control means actuator is operatively energized to energize the blower; electrically energizable timing means, circuit means controlled by said control means effective to operatively energize said timing means upon energization of said control means actuator, and means controlled by said timing means adapted a time period after energization thereof to energize the fuel burner and to operatively energize said safety cutout means actuator to thereby initiate said time period of operative energization of said safety cutout means actuator.

2. Burner control apparatus for use with a fuel burner unit having a fuel burner and a blower to supply air thereto for the purpose of both purging the fuel burner unit and supplying combustion air, the apparatus comprising; control means having an electrically energizable actuator and adapted upon energization thereof to energize the blower; safety cutout means having an electrically energizable actuator and having cutout means connected in controlling relationship to the control apparatus, said cutout means being adapted to be actuated after a time period of operative energization of said safety cutout means actuator to thereby render the fuel burner inoperative; a source of voltage circuit means connecting said control means actuator and said safety cutout means actuator in series to said source of voltage, the impedances of said actuators being such that while connected in series said safety cutout means actuator is operatively de-energized and said control means actuator is operatively energized; timing means having an electrically energizable actuator, circuit means controlled by said control means connecting said timing means actuator to a source of voltage thereby operatively energizing the same upon energization of said control means actuator; further means controlled by said timing means and effective a time period after energization of said timing means actuator to energize the fuel burner, to establish a maintaining circuit for said control means actuator, and to operatively energizesaid safety cutout means actuator to thereby initiate said time period; combustion sensing means adapted to sense the presence or absence of combustion at the fuel burner, and means controlled by said combustion sensing means connected in controlling relation to said safety cutout means actuator to operatively de-energize the same upon establishment of combustion at the fuel burner.

3. Burner control apparatus for use with a fuel burner unit having a burner adapted to support flame and having a fan adapted to supply air to the combustion chamber wherein the burner is located, the apparatus comprising; means responsive to the need for operation of the burner, a source of voltage, a relay having an actuating winding and switch means, safety cutout means having an electrically energizable actuator and a normally closed switch, circuit means controlled by said means responsive to the need for operation of the burner connecting said safety cutout means actuator and said relay winding in a series circuit to said source of voltage, the impedances of said relay winding and said actuatortbeing such that while connected in said series circuit said relay winding is operatively energized while said actuator is operatively de-energized, circuit means controlled by said relay switch means adapted to energize the fan, a timer having an electrically energizable actuator and switch means controlled thereby, further circuit means controlled by said relay switch means adapted to energize said timer actuator, circuit means controlled by said relay switch means and said timer switch means adapted to energize the burner after a purge period during which the fan supplies air to the combustion chamber to purge the combustion chamber of unburned fuel, and further timer switch means effective to operatively energize said safety cutout means actuator after the end of said purge period.

4. Burner control apparatus for use with a fuel burner having means to supply combustion air thereto, comprising; fiame sensing means adapted to sense the presence or absence of combustion at the fuel burner and having a switch closed in the absence of combustion, a relay having a winding and switch means, cutout means having an electrically energizable actuator and a normally closed switch, a transformer having a first and a second winding, means connecting said first winding to a source of operating voltage; circuit means connecting said flame sensing means switch, said cutout means actuator, said second transformer winding, said cutout means switch, and said relay winding in a series circuit to a source of operating voltage, the impedances of said cutout means actuator and said relay winding being such that while connected in said series circuit said cutout means actuator is operatively de-energized; circuit means controlled by said relay switch means adapted to energize the means to supply combustion air, a purge timer having switch means, circuit means controlled by said relay switch means adapted to energize said timer, circuit means jointly controlled by said relay switch means and said timer switch means adapted to energize the fuel burner a time period after energization of said timer, and circuit means controlled by said timer switch means adapted to connect said cutout means actuator and said flame sensing means switch in series across said second transformer winding to thereby operatively energize said cutout means actuator upon energization of the fuel burner, said cutout means actuator being operatively de-energized upon said flame sensing means sensing the presence of combustion at the fuel burner.

5. In combination, a fuel burner having a value and ignition means to ignite fuel present at the fuel burner, a fan to supply air to the vicinity of the fuel burner; a control relay having a winding and switch means controlled in accordance with the state of energization of said winding; safety cutout means having a heater, a bimetal associated with the heater, and a normally closed switch controlled by the bimetal; flame sensing means positioned to sense the presence or absence of flame at: the fuel burner and having switch means controlled in accordance therewith; initial energizing circuit means for said control relay winding including in a series circuit therewith said cutout means heater, said cutout means switch, and switch means of said flame sensing means which are closed when a flame is not present at the fuel burner, the impedance of said control relay winding being such that while connected in said series circuit said heater is operatively de-energized while said control relay winding is operatively energized; circuit means controlled by said control relay switch means effective to energize said fan; a timer having switch means controlled thereby, circuit means controlled by said control relay switch means effective to energize said timer; circuit means controlled by said timer switch means eifective to energize said ignition means and said valve a time period after energization of said timer, and further timer switch means effective to maintain said control relay winding energized and to operatively energize said cutout means heater a time period after energization of said timer.

6. In combination, a fuel burner having a valve and ignition means to ignite fuel present at the fuel burner, a fan to supply air to the vicinity of the fuel burner to first purge the burner and then supply combustion air, a relay having a winding and switch means controlled in accordance with the state of energization of said winding, flame sensing means positioned to sense the presence or absence of flame at the fuel burner and having flame sensing switch means closed in the absence of flame, initial energizing circuit means for said relay winding including in series therewith said flame sensing switch means to maintain said relay winding energized during a purge period, circuit means controlled by said relay switch means effective to energize said fan to institute the purge period, a timer having switch means controlled thereby, circuit means controlled by said relay switch means effective to energize said timer, circuit means including said timer switch means effective to energize said ignition means and said valve at the end of the purge period, and further circuit means including said timer switch means effective to maintain said relay Winding energized at the end of the purge period independent of said flame sensing switch means.

7. Burner control apparatus for use with a fuel burner unit having a fuel burner and means to supply air thereto, the apparatus comprising; safety cutout means having an electrically energizable actuator, control means having an electrically energizable actuator, timing means controlled by said control means and effective to institute a purge timing period to supply air to purge the fuel burner unit of unburned fuel after which timing period fuel is ignited at the fuel burner, a source of voltage, energizing circuit means for said control means actuator including in a series circuit said cutout means actuator and said control means actuator connected to said source of voltage, the impedances of said control means actuator and said cutout means actuator being such that while connected in said series circuit said cutout means actuator is maintained ctperatively de-energized, and further means con trolled by said timing means and effective to operatively energize said cutout means actuator after the fuel burner unit has been purged of unburned fuel.

References Cited in the file of this patent UNITED STATES PATENTS 2,727,568 Smith Dec. 20, 1955 2,748,845 Marshall et al. June 5, 1956 2,751,972 Loeber June 26, 1956 

1. BURNER CONTROL APPARATUS FOR USE WITH A FUEL BURNER UNIT HAVING A FUEL BURNER AND A BLOWER TO SUPPLY AIR THERETO FOR PURPOSES OF FIRST PURGING THE FUEL BURNER UNIT OF UNBURNED FUEL PRIOR TO THE IGNITION OF THE FUEL BURNER AND TO THEREAFTER SUPPLY COMBUSTION AIR, THE APPARATUS COMPRISING; CONTROL MEANS HAVING AN ELECTRICALLY ENERGIZABLE ACTUATOR AND ADAPTED UPON ENERGIZATION THEREOF TO ENERGIZE THE BLOWER; SAFETY CUTOUT MEANS HAVING AN ELECTRICALLY ENERGIZABLE ACTUATOR AND HAVING MEANS ADAPTED TO BE ACTUATED AFTER A TIME PERIOD OF OPERATIVE ENERGIZATION OF SAID ACTUATOR; A SOURCE OF VOLTAGE, ENERGIZING CIRCUIT MEANS FOR SAID CONTROL MEANS ACTUATOR CONNECTING SAID SAFETY CUTOUT MEANS ACTUATOR IN SERIES WITH SAID CONTROL MEANS ACTUATOR TO SAID SOURCE OF VOLTAGE, THE IMPEDANCES OF SAID ACTUATORS BEING SUCH THAT WHILE CONNECTED IN SERIES SAID SAFETY CUTOUT MEANS ACTUATOR IS MAINTAINED OPERATIVELY DEENERIZED WHILE SAID CONTROL MEANS ACTUATOR IS OPERATIVELY ENERGIZED TO ENERGIZE THE BLOWER; ELECTRICALLY ENERGIZABLE TIMING MEANS, CIRCUIT MEANS CONTROLLED BY SAID CONTROL MEANS EFFECTIVE TO OPERATIVELY ENERGIZE SAID TIMING MEANS UPON ENERGIZATION OF SAID CONTROL MEANS ACTUATOR, AND MEANS CONTROLLED BY SAID TIMING MEANS ADAPTED A TIME PERIOD AFTER ENERGIZATION THEREOF TO ENERGIZE THE FUEL BURNER AND TO OPERATIVELY ENERGIZE SAID SAFETY CUTOUT MEANS ACTUATOR TO THEREBY INITIATE SAID TIME PERIOD OF OPERATIVE ENERGIZATION OF SAID SAFETY CUTOUT MEANS ACTUATOR. 